Simulations of the Martian upper atmosphere have been produced from a self consis tent three dimensional numerical model of the Martian thermosphere and ionosphere called MarTIM. This model has been developed at UCL to cover an altitude range of 60km - 250km+. A radiation scheme is included that allows the main sources of heat input, EUV/UV and IR absorption by CO2 and CO, to be calculated. MarTIM self consistently calculates the composition of three of the main gases, CO2, N2 and 0, which are mutually diffused. These are treated as the major gases in the model. The other species densities (the minor gases), CO, Ar, O2 and NO, are based on dif fusive equilibrium above the turbopause. The ionosphere is calculated from a simple photoionisation and charge exchange routine which yields a peak electron density of around 2 TO5cm-3 at 135km, for Ls=0, solar minimum conditions. The semi-diurnal (2,2) migrating tide has been simulated and the results are presented and discussed. Comparisons of the model output to the available measurements from Mars Global Surveyor and Mars Pathfinder demonstrate that the fundamental parameters are well modelled and point to opportunities for further development. The fixed lower bound ary in the basic MarTIM was altered by using output from the Mars Climate Database as the lower boundary. The effects of this change at higher, thermospheric altitudes, has been calculated and reveals a significant dependence on this lower atmosphere input.

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Spacecraft sent to Mars have revealed that some ancient martian environments were habitable for life. Attempting to detect the organic matter that this potential life may have left behind has been a priority for several missions. However, the search for both biotic and abiotic organic compounds on Mars has yielded only organochlorines, which have an ambiguous origin. Recently it has been recognised that perchlorate (ClO4-) salts found on the surface of Mars are interfering with the heating experiments used by rovers and landers to search for organic matter. The potential for other oxygen-containing salts to disrupt thermal experiments has received comparatively little attention. In this thesis it is shown that the iron sulfate mineral jarosite thermally decomposes and releases oxygen at temperatures that would interfere with the detection of macromolecular organic matter. Experiments using synthetic jarosite samples revealed that during thermal decomposition sulfur dioxide and oxygen are released concurrently at a ratio of 2:1. In the presence of organic matter only the sulfur dioxide is detected, along with the carbon dioxide resulting from the combustion of carbon compounds. Prolonged exposure to water eventually causes jarosite to decompose into goethite. It was found that goethite can retain organic matter that was originally preserved in jarosite. The results demonstrate that though jarosite should be considered a problematic mineral for thermal experiments on Mars, goethite deposits in close proximity to jarosite may be good targets for organic matter detection. Jarosite and goethite have been observed on Mars by both rovers and orbiters. The transition from a habitable world to the present environment was marked by volcanism that created jarosite-forming, acidic, sulfur-rich conditions. The improved knowledge of the thermal extraction of jarosite and goethite containing samples will therefore be relevant in the analysis of a significant part of Mars’ geological history.

This thesis presents the development and application of a grid-based mapping approach that provides an efficient solution to the problems of mapping small landforms over large areas. The approach allows the cataloguing of landform classes, of multiple sizes, efficiently in a single pass. The speed at which the data could be recorded allowed for the first continuous, full resolution mapping of decametre-scale landforms in CTX images on hemispherical-scale maps. The discrete, tabular nature of grid mapping opens up the possibility of citizen science meaning the grid mapping approach could have considerable future use and impact. The main scientific goal of this thesis was to determine the distribution and origins of ice-related landforms in the northern plains, and provide insight as to whether these landforms are related to distinct geological or geomorphological units. To accomplish this, I used the grid mapping approach to explore a large tract covering the Arcadia Planitia region of the northern plains of Mars. In addition, I was able to compare these results to two other sister studies performed in the Utopia and Acidalia Planitia regions of Mars. To explore possible sources of ice I performed a detailed study of the Rahway Vallis system. This found an assemblage of terraces, channels and sinuous ridges in Rahway Vallis that are topographically and morphologically consistent with either a draining lake, or a melting, once liquid, ice-body, and is indicative of a flow of volatiles into the northern plains and large scale shifts in ground ice stability. Overall, this thesis demonstrates the dominant effects of the deposition and sublimation of the Latitude Dependent Mantle in shaping recent landscapes on the northern plains of Mars. There was little evidence for thaw-related landforms, and evidence for a fluvial origin for ice in the near surface is circumstantial, or has been erased or covered.

This thesis is concerned with the Beagle 2 X-ray spectrometer (XRS) for Mars. The scientific goals of the XRS were to perform (i) geochemical analyses of Martian rocks and soils and (ii) in situ 40K >40Ar dating of rocks. The major aims of this study were the development of the XRS to achieve its scientific goals and to inform the design of future versions of the instrument. The XRS is described and compared with the previous X-ray Spectrometers that have been successfully deployed on Mars. A characterisation of the XRS investigated the fundamental behaviour of the instrument in terms of its spectral features (gain, resolution and artefacts), gain variation with temperature of its components, deadtime and quantum efficiency. The XRS was calibrated to convert elemental intensities from its analyses into concentrations. The concentrations of several major and trace elements of interest in reference materials were linearly correlated with the certified concentration. The analytical performance of the XRS was evaluated in comparison with a terrestrial portable X-ray spectrometer (PXRF) and a wavelength dispersive X-ray spectrometer (WD XRF). The performance was characterised in terms of accuracy, detection limit and fitting precision. This study showed the importance of energy resolution to the analytical performance of the XRS. The operational performance of the XRS was evaluated. The geochemical composition of several basalts analysed by the XRS agreed with complementary analyses by the PXRF and WD XRF. The 40K >40Ar radiometric ages for two basalts were determined using the K content in the basalts in conjunction with their 40Ar isotope content (analysed by a laboratory version of the Beagle 2 Gas Analysis Package). The 40K 40Ar ages were found to differ to the Ar-Ar ages because of various effects associated with inhomogeneity of the K content in the rock and radiogenic40Ar loss.

The scientific exploration of Mars is currently being undertaken with the goals: to determine if Mars ever supported life; to understand the past and present climate; and to understand the evolution of its surface and interior. To achieve these goals, orbital and in-situ exploration of Mars is required. Detailed orbital high-resolution hyperspectral, image and topographic datasets enable the identification of areas of scientific interest on the surface of Mars. In-situ measurements are then taken by planetary landers and rovers to characterise the environment in great detail. This thesis has used orbital datasets to investigate impact craters on Mars, and has also focused on the development of a novel X-ray diffraction instrument technique that could be used to characterise the surface of Mars in-situ. The study of post-Noachian impact craters with hyperspectral data returned by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), highlighted two impact craters that may have hosted an impact-induced hydrothermal system. One of these impact craters shows spectral evidence for the presence of the mineral prehnite (Ca2Al2Si3O10(OH)2) that likely formed as a result of impact-induced hydrothermal activity, and might have provided a habitable environment for microbial life. A novel back-reflection X-ray diffraction technique that is uniquely insensitive to sample morphology, facilitating the analysis of unprepared whole-rock samples, was successfully tested on a range of samples from rock-forming minerals to carbonates, sulphates and phyllosilicates. A range of experimental facilities were utilised in this work, including a beamline at the Diamond Light Source synchrotron facility where the technique was further validated in a high-resolution configuration. The work presented in this thesis exemplifies the identification of an area of scientific interest on Mars, and the extensive testing and development of an instrument technique that could be used to geologically characterise such an identified area in-situ.

The discovery of water ice by the Phoenix Mars lander in 2008 and gypsum by Opportunity Rover in 2011 provides evidence that Mars was once a wet environment and therefore it could have sustained life in the past. Subsurface microbial life may be thriving on present Mars. The use of pyrolysis to liberate potential organic matter on Mars is known to cause mineral matrix-analytes interaction and result in total absence of detectable compounds. Solvent based extraction techniques were explored as alternatives to conventional pyrolysis for future Mars missions. Subcritical water extraction outperformed surfactant extraction but lagged behind organic solvent extraction where Martian regolith analogue was used. The study also showed that the optimum conditions of subcritical water extraction are an extraction temperature of 300 oC and an extraction duration of 20 minutes. Molecular transformations under hot aqueous conditions were also observed in the same study, for instance, the structural change of anthracene to aromatic diketone. Subcritical water extraction of organic matter bearing sedimentary rocks produced a range of organic compounds diagnostic of microbial and plant materials. The outcomes of subcritical water extraction of sedimentary rocks can help predict the subcritical water treatment responses of biotic chemical classes that may still survive on Mars. The chemical structures of plant organic compounds are similar to chemical structures of meteoritic macromolecules and the results of subcritical water extraction of type III organic matter can help distinguish the abiotic organic compounds from the biotic hydrocarbons on Mars. Further subcritical water experimentation using sulphate and iron rich samples collected from a low pH environment demonstrated the habitability of sulphate and iron rich environments on Mars and the capability of subcritical water system to isolate useful organic biosignatures from an active microbial community with inputs of plant materials. A comparison between two different extraction modes of subcritical water showed the superior performance of the static mode compared to dynamic extraction. Heavy oil sand extraction using subcritical water provided further evidence of the usefulness of subcritical water technology beyond the realm of space research.

Mars is thought to have a planet-wide cryosphere of several kilometres depth consisting of a mixture of rock and permanently frozen ice. The physical processes occurring during magma-cryosphere interaction (MCI) appear to have played a large part in the morphological development of many regions of Mars. The aim of this thesis was to investigate the physical and thermal processes that may take place X during non-explosive MCI. A mass-balance heat-flow model was developed to determine if MCIs could have independently resulted in the formation of features seen on Mars. Laboratory analogue experiments were used to investigate the effects resulting from the heating of a cryosphere analogue over a range of conditions. Two phase (solid particles and liquid water or air) and three phase (solid particles of sand or ice, liquid water and steam) systems were investigated. This enabled the identification of several heat transfer mechanisms; the dominance of these mechanisms varied with the conditions in each experiment. The influence of different heat transfer mechanisms on the development of surface features was also studied. This research has highlighted the complexity of the heat transfer mechanisms and physical interactions that take place during non-explosive magma-cryosphere processes on Mars. We have determined that heat transfer mechanisms can have a significant directional component that results in specific experimental surface morphologies. Similarity to Martian landforms provides insight into their formation mechanisms. This research provides constraints to assist identification and classification of newly discovered landforms within Mars’ landscape.